Field of the Invention
The present invention relates to a vehicle headlamp unit for selectively irradiating light in accordance with a position of a forward vehicle or the like, and a vehicle headlamp system comprising the vehicle headlamp unit.
Description of the Background Art
Conventionally, there have been known vehicle headlamp systems that set an irradiation range and a non-irradiation range of light from a headlamp unit of a vehicle in accordance with a position of an oncoming vehicle or a preceding vehicle that exists in front of the vehicle (hereinafter simply referred to as “forward vehicle”).
A precedent example related to such a vehicle headlamp system is disclosed in Japanese Unexamined Patent Application Publication No. 07-108873 (hereinafter referred to as “Patent document 1”), for example. According to this type of vehicle headlamp system, a camera is installed in a predetermined position of the vehicle (in a center upper area of a front windshield, for example), and a position of a vehicle body, a tail lamp, or a headlamp of a forward vehicle captured by the camera is detected by image processing. Then, light distribution control is performed so that light from the headlamp units of its own vehicle is not irradiated in a section of the detected forward vehicle.
Further, as a precedent example of a vehicle headlamp that can be applied to light distribution control such as described above, a vehicle headlamp that utilizes a liquid crystal element is disclosed in Japanese Translation of PCT International Application Publication No. JP-T-2009-534790 (hereinafter referred to as “Patent document 2”), for example. The lamp unit for a vehicle adaptive front lighting system disclosed in this document is a lamp unit that includes a liquid crystal element configured to receive light emitted by a light source, wherein the liquid crystal element has, when light passes through the liquid crystal element, a first state configured so that incident light is transmitted through without substantial refraction, and a second state configured so that the incident light is refracted, and the liquid crystal element is controlled based on a signal received from the adaptive front lighting system.
However, in the precedent example according to Patent Document 2, while the vehicle headlamp uses an element that utilizes refraction and scattering as the liquid crystal element, the liquid crystal element has a low light-dark ratio (contrast ratio) compared to a liquid crystal element for a display (liquid crystal display element) used in a liquid crystal television or the like, and is thus not always capable of sufficiently cutting off the illumination light when utilized for light distribution control of a vehicle headlamp, leaving room for improvement.
It is therefore an object of specific aspects according to the present invention to provide a vehicle headlamp unit and the like that have a high contrast ratio of light and dark light, and are capable of sufficiently cutting off the illumination light.